Deep Horizon Oil Spill: Impacts on Costal Plant Communities

Dr. Jessie C. Jarvis

Marine Science Program

The Richard Stockton College of New Jersey

Gulf Coast Aquatic Plant Communities

• Louisiana contains ~7,200 mi2 of wetlands– 12% of the nation's coastal

wetlands

• Emergent habitats:– Salt marsh/black mangrove

• Submerged habitats:– Seagrass

• Ecological functions:– Habitat/nursery grounds

– Food source

– Storm protection

– Increase water quality

Emergent Wetland SpeciesSpartina alterniflora

Smooth Cordgrass

Avicennia germinans

Black Mangrove

Seagrass Species

Thalassia testudinum

Turtle grass

Syringodium filiforme

Manatee grass

Threats Prior to BP Spill• Under severe stress before Deep Horizon oil spill

• Since 1956 ~ 1 million acres of coastal marsh has been lost in LA– Average loss of 16,000 acres yr-1

• 1990 - 2001, wetland loss in LA was equivalent of one football field lost every hour

• Seagrass loss due to:– Boat propeller scars

– Boat groundings

– Sediment burial (storms)

Coastal Areas Affected by Direct Oiling Events

Combined oil spill slick area May 8 – Aug 7

Amount of oil found on shoreline*

low

moderate

high

* Data from U.S. Fish and Wildlife Service; National Oceanic and Atmospheric Administration; National Park Service; state and local officials; NY Times

BarratariaBasin

Gulf of Mexico

ChandeleurIslands

Estimated that between 0.8 to 3.4 mi2 of Gulf Coast was oiled

NOAA

Effects of Oil on Aquatic Plants

• Impact can vary depending upon:– Affected species

– Amount of oil

– Characteristics of oil

– Extent of weathering

– Number of oil events

– Soil penetration*

• Complicated by other stressors– Subsidence

– Sea level rise

Effects of Oil on Emergent Wetlands

• Soil penetration is key factor

• Rely on belowground rhizomes (underground stems) for new shoot production every year

• Leaves /shoots can die and plant survive ifrhizomes survive

Rhizomes

Oiled Marsh in LA

Oil soaking into sediment

Oiled grasses may die-back but survive if rhizomes survive

Effects of Oil on Wetlands

• If oil penetrates sediment then rhizomes may die

• If rhizomes die:

– Soil compacts and collapses

– Soil elevation too low for plant recolonization

– Open water area created

– Erosion increases in surrounding marsh

– More rhizomes die USGS

Effects of Oil on Seagrass• The water soluble fraction of oil negatively

affects seagrass– Dispersants increase bioavailability (Thorhaug et al., 1986)

– Break down waxy cuticle = greater exposure to hydrocarbons

– Sub-lethal effects make plants more susceptible to other stressors

• Other oil spills show limited short term (<1 yr) negative effects– Long term effects unknown(Kenworthy et al., 1993)

Direct Clean-Up ResponsesDo (Almost) Nothing Low-Pressure Wash

• Skim oil from surface with skimmer

• Manually wash shoots with low-pressure hose

• Potential impacts from:– Walking through wetland

– Vehicles with hoses

• Put out booms

• Skim off oil that can be reached by boat

• Depend upon rhizomes to produce new shoots

Direct Clean-Up ResponsesBurning Natural Additives

• Soak up between 3-15 times their weight

• May sink and be difficult to collect

• Examples: peat moss, straw, sawdust, feathers, ground corncobs

• Removes almost all oil

• Maximum results during time of senescence

• Amount of water on marsh has impact on rhizome survival

Current Status

• Immediate short term impacts comparable to other smaller events– Next spring real test

• Some loss of area but not the catastrophic decline predicted

• Small areas of recovery already observed

• Need for long term monitoring

Thank you

Contact Information:

Jessie Jarvis, PhD

NAMS – Marine Science

The Richard Stockton College of New Jersey

P.O. Box 195

Pomona, NJ 08240

Phone: 609-652-4249

Email: jessie.jarvis@stockton.edu

Conclusions

• Greater impact on intertidal than subtidal aquatic plant communities– Next spring earliest to begin to understand how oil

spill impacted wetlands

• Based on the characteristics of this oil spill may be best to take the “Do (Almost)Nothing” approach

• Need for immediate action can lead to greater problems

• Restoration need already great in LA marshes

• Future monitoring of affected areas is essential